U.S. patent number 10,604,622 [Application Number 16/002,067] was granted by the patent office on 2020-03-31 for composition crosslinkable by real michael addition (rma) reaction.
This patent grant is currently assigned to Allnex Netherlands B.V.. The grantee listed for this patent is ALLNEX NETHERLANDS B.V.. Invention is credited to Richard Hendrikus Gerrit Brinkhuis, Elwin Aloysius Cornelius Adrianus De Wolf, Ferry Ludovicus Thys.
United States Patent |
10,604,622 |
Brinkhuis , et al. |
March 31, 2020 |
Composition crosslinkable by Real Michael Addition (RMA)
reaction
Abstract
A crosslinkable composition crosslinkable by Real Michael
Addition (RMA) reaction comprising a component with at least 2
activated unsaturated groups and a component with at least 2 acidic
protons C--H in activated methylene or methine which components can
react to form a crosslinked network.
Inventors: |
Brinkhuis; Richard Hendrikus
Gerrit (Zwolle, NL), Thys; Ferry Ludovicus
(Stevens-Woluwe, BE), De Wolf; Elwin Aloysius Cornelius
Adrianus (Hoogerheide, NL) |
Applicant: |
Name |
City |
State |
Country |
Type |
ALLNEX NETHERLANDS B.V. |
Bergen op Zoom |
N/A |
NL |
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Assignee: |
Allnex Netherlands B.V. (Bergen
op Zoom, unknown)
|
Family
ID: |
48045350 |
Appl.
No.: |
16/002,067 |
Filed: |
June 7, 2018 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20180282477 A1 |
Oct 4, 2018 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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14781600 |
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10017607 |
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PCT/EP2014/056953 |
Apr 7, 2014 |
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Foreign Application Priority Data
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Apr 8, 2013 [EP] |
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13162819 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08G
63/916 (20130101); C08J 3/24 (20130101); C09D
167/02 (20130101); C08G 63/181 (20130101); C08K
3/013 (20180101); C08G 63/91 (20130101); C08J
2367/00 (20130101) |
Current International
Class: |
C08G
63/91 (20060101); C09D 167/02 (20060101); C08J
3/24 (20060101); C08G 63/181 (20060101); C08K
3/013 (20180101) |
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|
Primary Examiner: Pepitone; Michael F
Attorney, Agent or Firm: Hoyng Rokh Monegier LLP Amirsehhi;
Ramin
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATION
This application is a divisional of Ser. No. 14/781,600 filed on
Oct. 1, 2015, which granted on Jul. 10, 2018 as U.S. Pat. No.
10,017,607, which is a 371 of PCT application number
PCT/EP2014/056953 filed on Apr. 7, 2014, which claims priority from
EP application number 13162819.0 filed on Apr. 8, 2013. All
applications are hereby incorporated by reference in their
entireties.
Claims
What is claimed is:
1. A kit of parts for manufacturing a crosslinkable composition
crosslinkable by Real Michael Addition (RMA) reaction, wherein the
crosslinkable composition comprises: a) Component(s) A having at
least 2 acidic C--H donor groups in activated methylene or methine
and having a pKa(A) between 10.5 and 14, b) Component(s) B having
at least 2 activated unsaturated acceptor groups, wherein a molar
ratio R of acceptor groups to donor groups is between 3:1 to 1:6
and which component(s) B react with component(s) A by Real Michael
Addition (RMA) to form a crosslinked network, c) basic component(s)
C being a salt of a basic anion X-- from an acidic X--H group
containing compound wherein X is N, P, O, S or C, i) in an amount
xc between 0.001 and 1 meq/(gr of components A, B, C), ii) anion
X-- being a Michael Addition donor reactable with component B and
iii) anion X-- is characterized by a pKa(C) of the corresponding
acid X--H of more than two units lower than the pKa(A) of the
majority component A and being lower than 10.5, wherein the
majority component A is the component A providing at least 50 mole
% of the C--H acidic RMA donor groups, wherein the kit comprises 1)
a part I.1, comprising component C and a part II.1 not comprising
component C and comprising components A, B or alternatively 2) a
kit of parts comprising a part I.2 comprising component C,
component A, but not comprising component B and part II.2
comprising component B or alternatively 3) a kit of parts
comprising part I.3 comprising components A, B and instead of
component C the corresponding acidic compound X--H and a part II.3
comprising a strong base for mixing with part I.3.
2. The kit of claim 1, wherein the crosslinkable composition
comprises: component(s) D comprising one or more acidic X'--H
groups wherein X' is N, P, O, S or C, i) X' being a same or
different group as group X in component C, ii) the X'-- anion being
a Michael Addition donor reactable with component B, iii) the
pKa(D) of the X'--H group in component D being more than two units
lower than pKa(A) of the majority component A and being lower than
10.5, iv) the equivalent ratio Rd/c of acidic X'--H groups in
component D over basic anion X-- in component C is between 1 and
5000%, wherein the kit comprises: a part I.1, comprising component
C and at least part of component D and a part II.1 not comprising
component C and comprising components A, B and D or alternatively
2) a kit of parts comprising a part I.2 comprising component C,
component A, and at least a part of component D but not comprising
component B and part II.2 comprising component B and components D
or alternatively 3) a kit of parts comprising part I.3 comprising
components A, B, D and instead of component C the corresponding
acidic compound X--H and a part II.3 comprising a strong base for
mixing with part I.3.
3. The kit of claim 2, wherein the composition and the kit do not
comprise an ethylmalonate modified polyester based on neopentyl
glycol and hexahydrophthalic anhydride,
di-trimethylolpropane-tetraacrylate and tetrabutylammonium
succinimide and ethylacetoacetate.
4. The kit of claim 2, wherein pKa(D) is equal to or higher than
pKa(C).
5. The kit of claim 1, wherein the crosslinkable composition
further comprises component(s) F comprising an acidic X''--H group
wherein X'' is N, P, O, S or C i) different from components A, ii)
F being a Michael addition donor reactable with component B,
wherein the kit comprises: 1) a part I.1, comprising component C
and a part II.1 not comprising component C and comprising
components A, B and F or alternatively 2) a kit of parts comprising
a part I.2 comprising component C, component A, optional solvents
but not comprising component B and part II.2 comprising component B
and component F or alternatively 3) a kit of parts comprising part
I.3 comprising components A, B and F and instead of component C the
corresponding acidic compound X--H and a part II.3 comprising a
strong base for mixing with part I.3.
6. The kit of claim 1, wherein the composition comprises less than
50 mole % and relative to basic components C of other basic
compound other than C that can initiate or catalyse the RMA
crosslinking reaction.
7. The kit of claim 1, wherein the crosslinkable composition
comprises: component(s) D and F, wherein the component D comprises
one or more acidic X'--H groups wherein X' is N, P, O, S or C, i)
X' being a same or different group as group X in component C, ii)
the X'-- anion being a Michael Addition donor reactable with
component B, iii) the pKa(D) of the X'--H group in component D
being more than two units lower than pKa(A) of the majority
component A and being lower than 10.5, iv) the equivalent ratio
Rd/c of acidic X'--H groups in component D over basic anion X-- in
component C is between 1 and 5000%, and wherein the component F
comprises an acidic X''--H group wherein X'' is N, P, O, S or C i)
different from components A and D, ii) F being a Michael addition
donor reactable with component B, wherein the kit comprises: 1) a
part I.1, comprising component C and a part II.1 not comprising
component C and comprising components A, B, D and F or
alternatively 2) a kit of parts comprising a part I.2 comprising
component C, component A, and at least a part of component D but
not comprising component B and part II.2 comprising component B and
other components D and F or alternatively 3) a kit of parts
comprising part I.3 comprising components A, B, D and F and instead
of component C the corresponding acidic compound X--H and a part
II.3 comprising a strong base for mixing with part I.3.
8. The kit of claim 7, comprising: a) Component(s) A in an amount
xa between 5 and 95 wt %, b) Component(s) B in an amount xb between
5 and 95 wt %, wherein xa plus xb is at least 40 wt %, c) basic
component(s) C in an amount xc between 0.001 and 1 meq/(gr total
resin), d) component(s) D in an amount xd such that the equivalent
ratio Rd/c of acidic X'--H groups in component D over basic anion
groups X- in component C is between 0% and 5000%, e) component(s) F
in an amount xf between 0 and 30 wt %, wherein wt % is relative to
total resin forming components A, B, C, D and F.
9. The kit of claim 1, wherein at least 50 mole % of the RMA donor
groups in component(s) A are from malonate or acetoacetate
groups.
10. The kit of claim 1, wherein components B are acryloyl or
maleate groups or mixtures thereof.
11. The kit of claim 2, wherein anions X- and X'- in components C
and D have a lower Michael Addition reactivity towards component B
than an anion of the majority component A by a factor of at least
3, but no more than 10,000.
12. The kit of claim 2, wherein a) more than 50 mole % of RMA donor
groups in components A are from malonate groups, b) more than 50
mole % of the RMA acceptor groups in component B are from acryloyl
groups, c) component C is a benzotriazolide salt, a salt of
1,2,4-triazole or a salt of 1,3-cyclohexanedione, and d) component
D is benzotriazole or a triazole, a 1,3-diketone, or an imid.
13. The kit of claim 2, wherein the anion X- in component C, and/or
the X' group in component D is an aza-acidic compound (X=N)
comprising a molecule containing the N--H as part of a group
Ar--NH--(C.dbd.O), --(C.dbd.O)--NH--(C.dbd.O)--, or a
--NH--(O.dbd.S.dbd.O)-- group, or a heterocycle in which the
nitrogen of the N--H group is contained in a heterocyclic ring, or
a cyclic imide, or substituted succinimide or a triazole
component.
14. The kit of claim 2, wherein the anion X- from component C,
and/or the X' group in component D is a carbon-acidic compound
(X=C).
15. The kit of claim 2, wherein the anion X- in component C, and/or
the X' group in component D are derived from an aromatic
sulfonamide.
16. The kit of claim 2, wherein component C is a triazole and
component D an imid or a 1,3 diketone.
17. A coating composition comprising paint additives, and a
crosslinkable composition comprising: a) Component(s) A having at
least 2 acidic C--H donor groups in activated methylene or methine
and having a pKa(A) between 10.5 and 14, b) Component(s) B having
at least 2 activated unsaturated acceptor groups, wherein a molar
ratio R of acceptor groups to donor groups is between 3:1 to 1:6
and which component(s) B react with component(s) A by Real Michael
Addition (RMA) to form a crosslinked network, c) basic component(s)
C being a salt of a basic anion X-- from an acidic X--H group
containing compound wherein X is N, P, O, S or C, i) in an amount
xc between 0.001 and 1 meq/(gr of components A, B, C), ii) anion
X-- being a Michael Addition donor reactable with component B and
iii) anion X-- is characterized by a pKa(C) of the corresponding
acid X--H of more than two units lower than the pKa(A) of the
majority component A and being lower than 10.5.
18. A composite article comprising a filler material and as a
binder material a crosslinked composition comprising: a)
component(s) A having at least 2 acidic C--H donor groups in
activated methylene or methine and having a pKa(A) between 10.5 and
14, b) component(s) B having at least 2 activated unsaturated
acceptor groups, wherein a molar ratio R of acceptor groups to
donor groups is between 3:1 to 1:6 and which component(s) B react
with component(s) A by Real Michael Addition (RMA) to form a
crosslinked network, c) basic component(s) C being a salt of a
basic anion X- from an acidic X--H group containing compound
wherein X is N, P, O, S or C, i) in an amount xc between 0.001 and
1 meq/(gr of components A, B, C), ii) anion X-- being a Michael
Addition donor reactable with component B, and iii) anion X-- is
characterized by a pKa(C) of the corresponding acid X--H of more
than two units lower than the pKa(A) of the majority component A
and being lower than 10.5.
Description
The present invention relates to a crosslinkable composition
crosslinkable by Real Michael Addition (RMA) reaction comprising a
component with at least 2 activated unsaturated groups (hereafter
referred to as the RMA acceptor groups) and a component with at
least 2 acidic protons C--H in activated methylene or methine
groups (hereafter referred to as the RMA donor groups) which
components can react to form a crosslinked network.
RMA chemistry can be tuned to give fast curing compositions, also
at lower curing temperatures, in compositions at acceptable or good
pot lives, to achieve good material properties, which makes this
chemistry very attractive as a basis for crosslinkable
compositions. Details of RMA cross-linkable compositions using a
latent base crosslinkable catalyst are described in
WO2011/124663.
Real Michael addition is activated by strong bases, but also
inhibited by the presence of acidic species that will consume these
basic catalysts. In tuning the reactivity of coating systems in
view of achieving a desirable drying profile, there are various
requirements to balance. The drying profile (also referred to as
the reaction profile or as the curing profile) is the progress of
the crosslinkable reaction as a function of time. Generally, it is
required that the drying profile allows build-up of mechanical
properties as fast as possible, under mild conditions, to help the
productivity. The crosslinkable composition also requires a
reasonable time in which it can be used with good application
properties, following its formulation, for it to be practical; this
time is generally referred to as the pot life. It is further also
required to have a drying profile that is robust, i.e. the
reactivity (and hence the resulting drying profile) is not strongly
influenced by accidental low levels of acidic contaminants being
present.
On the other hand, for coating applications, it is required to have
a good appearance of the resulting coating. This implies the need
for sufficient levelling during the immediate period after
application, when the curing coating composition is present as a
liquid and capable of such levelling. This also implies the need
for absence of artefacts like solvent inclusions or gas inclusions
or other surface irregularities that may occur if curing is very
fast, especially if it is faster at the surface than in deeper
layers, which is often the case if curing occurs at the time scale
of solvent evaporation or surface activation of a catalyst. Also
film hardness build-up will be affected under conditions in which
solvent entrapment occurs.
The described requirements are to some extent opposing each other.
For a fast curing profile, but also for a high robustness against
accidental acid contaminants reasonably high levels of catalyst are
preferred, whereas at the same time such high levels of catalysts
may create a too rapid cure, and negatively influence surface
appearance and hardness development as described above. In general,
higher catalyst levels may also negatively affect the pot life.
It has been shown in previous publications WO2011/124663,
WO2011/124664, and WO2011/124665 that it is possible to combine
fast curing with a long pot life, by using carbon dioxide blocked
basic catalyst, that become active upon evaporation of carbon
dioxide (CO2) when the composition is applied as thin film. Whereas
this method is useful in creating long pot life/fast cure
combinations, it introduces complications in the case of thick
films applications, where there is a risk of inhomogeneous
activation resulting from CO2 escaping from the surface. Moreover,
for applications in which there is no large surface available for
allowing CO2 to evaporate, such CO2 blocked catalysts have
significant limitations.
There is also a desire for crosslinkable compositions that can be
simply cured in ambient conditions as opposed to for example
compositions comprising photo-latent amine catalysts, known from T.
Jung et al Farbe and Lacke October 2003. Such photo-latent amine
catalysts that do generate a strong base on UV radiation, are not
suitable for coating more complex irregular substrates where parts
of the surfaces are not reachable with UV or visible light, or for
highly pigmented systems.
The object of the invention is to provide an RMA cross-linkable
composition that provides a better balance in these counteracting
requirements.
According to the invention at least one of the aforementioned
problems has been overcome by a crosslinkable composition
crosslinkable by Real Michael Addition (RMA) reaction comprising a.
Component(s) A having at least 2 acidic C--H donor groups in
activated methylene or methine and having a pKa(A) between 10.5 and
14, b. Component(s) B having at least 2 activated unsaturated
acceptor groups, wherein a molar ratio R of acceptor groups to
donor groups is between 3:1 to 1:6 and which component(s) B reacts
with component(s) A by Real Michael Addition (RMA) to form a
crosslinked network, c. basic component(s) C being a salt of a
basic anion X-- from an acidic X--H group containing compound
wherein X is N, P, O, S or C, i. in an amount xc between 0.001 and
1 meq/(gr of components A, B, C, D), ii. anion X-- being a Michael
Addition donor reactable with component B and iii. anion X-- is
characterized by a pKa(C) of the corresponding acid X--H of more
than two units lower than the pKa(A) of the majority component A
and being lower than 10.5, d. optional component(s) D comprising
one or more acidic X'--H groups wherein X' is N, P, O, S or C, i.
X' being a same or different group as group X in component C, ii.
the X'-- anion being a Michael Addition donor reactable with
component B, iii. the pKa(D) of the X'--H group in component D
being more than two units lower than pKa(A) of the majority
component A and being lower than 10.5, iv. the equivalent ratio
Rd/c of acidic X'--H groups in component D over basic anion X-- in
component C is between 1% and 5000%, e. not including a composition
comprising an ethylmalonate modified polyester based on neopentyl
glycol and hexahydrophthalic anhydride,
di-trimethylolpropane-tetraacrylate and tetrabutylammonium
succinimide and ethylacetoacetate.
The inventors have found that it is possible to initiate an
effective cross-linking reaction between RMA donor and acceptor
components A and B using the specified component C being a salt of
a cation and a basic anion X-- from a (deprotonated) acidic X--H
group containing compound wherein X is N, P, O, S or C and wherein
anion X-- also is a Michael Addition donor reactable with component
B and with specific requirements for the pKa(C) of the
corresponding X--H. The specified anion X-- of component C
initiates the RMA reaction and anion X-- will be covalently linked
to component A and become integrated into the cross-linked network
being formed, which is advantageous in view of the mechanical and
chemical properties of the resulting crosslinked product. The term
acidic X--H group containing compound wherein X is N, P, O, S or C
means a compound comprising an X--H acidic group wherein the acidic
proton H is situated on a N, P, O, S or C atom in that compound.
Although the X here refers to an atom in the compound, where in the
description or claims reference is made to X--H group, anion X--,
group X-- etc it of course refers to the compound containing the
acidic X--H or deprotonated X-- group. This similarly applies to X'
and X''.
Whether or not a component is a Michael Addition donor reactable
with component B depends on the pKa values as specified, but also
on certain molecular parameters. Michael Addition donors are known
in literature and it can easily be established by the skilled
person by a simple experiment whether or not a component exhibits
Michael addition reactivity towards component B. Such experiment is
also described below. Suitable X--H group containing components
with their pKa values are also described below. Each component A,
C, D, and F in the composition is identified by a characteristic
range of pKa. The pKa values of both existing compounds are
reported in literature and/or can easily be established by standard
routine by the skilled person. In this context, where a component
comprises more than one acidic proton, the relevant pKa of said
component is the pKa of the first proton of the component; for
example pKa(A) from malonate is 13. Further, when referring to the
pKa of a component it is implied that reference is made to the pKa
of the X--H acidic RMA donor group in that component. It is noted
that the term component(s) means one or more components, which
includes also two or more different components.
The composition according to the invention provides a well-balanced
set of application properties as application time drying time,
hardness development without solvent entrapment complications and
appearance. The initiation of the RMA reaction does not require a
separate base catalyst. In particular, the RMA reaction for the
composition of the invention does not require a carbon dioxide
blocked base catalyst and therefore it has advantages in
applications like composites, adhesives etc where carbon dioxide
evaporation is problematic or impossible. Apart from that, the
composition can be significantly less expensive compared to
compositions having a latent base catalyst. One aspect of that
lower price is the wider choice of cations that can be used in the
salt component C, including less-expensive cations like alkaline or
alkaline earth metal cations, due to a better solubility of the
salt of most anions X-- compared to a carbonate anion. Yet another
advantage of the present invention is that the component C is less
sensitive to inhibition of RMA reaction by a hydroxyl groups
containing polymer. Therefore, the salt component C can be used in
combination with one or more A, B, D and/or F containing hydroxy
functional polymers having a hydroxy value of more than 61 mgr
KOH/gr and up to 200, 180, 150, 120 100 or 80 mgr KOH/gr, whilst
still having good appearance and hardening properties.
Disclaimed from the above composition is a composition comprising
an ethylmalonate modified polyester based on neopentyl glycol and
hexahydrophthalic anhydride, di-trimethylolpropane-tetraacrylate,
tetrabutylammonium succinimide and ethylacetoacetate.
Alternatively, the above composition does not include
tetrabutylammonium succinimide as component C in combination with
ethylacetoacetate. Alternatively, the composition does not comprise
tetrabutylammonium succinimide as component C.
In a preferred embodiment, the crosslinkable composition comprises
component(s) D comprising one or more acidic X'--H groups wherein
X' is N, P, O, S or C, i. X' being a same or different group as
group X in component C, ii. the X'-- anion being a Michael Addition
donor reactable with component B, iii. the pKa(D) of the X'--H
group in component D being more than two units lower than the
pKa(A) of the majority component A and being lower than 10.5, iv.
the equivalent ratio Rd/c of acidic X'--H groups in component D
over basic anion X-- in component C is between 1 and 5000%.
It was surprisingly found that the presence of component D in the
inventive composition creates a drying profile with an induction
time, implying that crosslinking reactivity starts off low
(allowing pot life, flow and escape of optional solvent), while
still benefiting from the full potential of the initiator component
C beyond this induction time, thus creating an acceleration of the
reaction at later stages to complete crosslinking at high rate.
This induction time can be tuned through the amounts and
characteristics of components C and D as will be explained in more
detail below.
Component D is optional, so the amount range is between 0% and
5000%. Preferably, component D is present and the equivalent ratio
Rd/c of acidic X'--H groups in component D over basic anion X-- in
component C is between 10 and 4000%, more preferably between 20 and
2000%, most preferably between 50 and 500%, 400% or 300% or between
75 and 200%.
Without wishing to be bound by theory it is believed that the
reaction mechanism in essence is that anion X-- in component C
reacts with B forming the deprotonated X--B-- carbanion adduct,
which on turn deprotonates X'--H groups in component D (the next
strongest acid available) to form anion X'-which on turn reacts
with B to form adduct X'--B-- until the amount of D has been
depleted and only then the strong base X'--B-- adduct will react
with A (which reacts later than D because A is less acidic and has
a higher pKa). The latest reaction in the reaction chain is the
reaction causing the components A en B to crosslink to form a
network. However, the time consuming reaction is the reaction
between anion X-- and X'-- with B to form adduct X--B-- and X'--B--
because the reactivity of anion X-- and X'-- towards B is low,
which creates the induction time.
Yet another advantage of the present invention compared to the
prior art CO2 blocked latent base catalyst is that the lower limit
of the pKa of the components in the composition can be much lower
because there is no risk of acid decomposition of the CO2 blocked
catalyst. The pKa(C) and pKa(D) can be very low. The pKa(C) and
pKa(D) can be as low as -2, -1, 0 but preferably are at least 1, 2
or 3 in view of achieving sufficient Michael addition reactivity.
Because of this wide pKa range the component C and D can be chosen
from a relatively wide range of molecules.
The initiation of the RMA reaction is caused by components C. The
composition according to the invention does not need any further
basic components to initiate the RMA reaction. Therefore, it is
preferred that the composition comprises less than 50 mole %, and
most preferably substantially no (i.e. 0 mole %) of another basic
compound other than C that can initiate or catalyse the RMA
crosslinking reaction. Preferably, the composition comprises less
than 50, 40, 30, 20, 15, 10, 5, 3 mole % relative to basic
components C of a basic component other than C that is able to
initiate (directly of after deblocking or activation) the RMA
reaction between A and B. In particular, it is an advantage of the
present advantage that the composition comprises substantially no
latent base catalyst, more in particular substantially no
carbondioxide blocked latent base catalyst. This allows application
in thicker layers or articles. An other base, for example an amine,
can be present as long as it is so weak a base that it will not
initiate RMA reaction.
In the component(s) A, the acidic C--H donor groups in activated
methylene or methine having a pKa(A) between 10.5 and 14 and
preferably have a structure according to formula 1:
##STR00001## wherein R is hydrogen or an alkyl, aralkyl or aryl
substituent and Y and Y' are same or different substituent groups,
preferably alkyl, aralkyl or aryl (R*), or alkoxy (--OR*) or
wherein the --C(.dbd.O)--Y and/or --C(.dbd.O)--Y' is replaced by CN
or phenyl. The activated methylene or methine is the
--(H--)C(--R)-- group between the carbonyl groups in Formula 1.
Preferably the RMA donor groups of component A are from malonate or
acetoacetate groups and preferably they are dominantly from
malonate groups. As these components can be build into a polymer
for example trough transesterification, the ester group therein can
be an ester link with a polymer.
In the crosslinkable composition it is preferred that the majority,
preferably at least 50, 60, 70, or even 80 mole % of the C--H
acidic RMA donor groups in component(s) A are from malonate or
acetoacetate groups, more preferably malonate groups. In this case
the malonate or acetoacetate groups are referred to as the dominant
component A. The term dominant refers to the compound providing the
majority of the functional RMA reactive donor or acceptor groups;
in case of component A, C, D and F the type of X--H containing
donor group providing the majority of the X--H acidic RMA donor
groups. In the crosslinkable composition the majority, preferably
at least 50, 60, 70 or even 80 mole % of the C--H acidic RMA donor
groups in component(s) A are from malonate groups with the
remaining RMA donor groups in component(s) A being substantially
only from acetoacetate groups.
Components A containing both malonate and acetoacetate groups in
the same molecule are also suitable. Additionally, physical
mixtures of malonate and acetoacetate group-containing components
are suitable. For example, components A could be a physical mixture
of a polymer comprising malonate and single acetoacetate molecules.
Especially preferred malonate group-containing components for use
with the present invention are the malonate group-containing
oligomeric or polymeric esters, ethers, urethanes and epoxy esters
containing 1-50, more preferably 2-10, malonate groups per
molecule. In practice polyesters and polyurethanes are preferred.
It is also preferred that such malonate group-containing components
have a number average molecular weight (Mn) in the range of from
about 100 to about 5000, more preferably, 250-2500, and an acid
number of about 2 or preferably less. Also monomalonates can be
used as they have 2 reactive C--H per molecule. Monomeric malonates
can, in addition, be used as reactive diluents.
Components B generally can be ethylenically unsaturated components
in which the carbon-carbon double bond is activated by an
electron-withdrawing group, e.g. a carbonyl group in the
alpha-position. Suitable components B are known in the art, for
example (meth-)acryloyl esters, (meth-) acrylamides, alternatively
polyesters based upon maleic, fumaric and/or itaconic acid (and
maleic and itaconic anhydride and polyesters, polyurethanes,
polyethers and/or alkyd resins containing pendant activated
unsaturated groups. Acrylates, fumarates and maleates are
preferred. Most preferably, the dominant component B, preferably
providing at least 50, 60, 70, 80 or even at least 90 mol % of the
RMA acceptor groups, is an unsaturated acryloyl functional
component. Preferably the functionality, defined as the number
average number of unsaturated RMA acceptor groups per molecule
component B, is 2-20, the equivalent weight (EQW: average molecular
weight per reactive functional group) is 100-2000, and the number
average molecular weight preferably is Mn 200-5000.
The amounts of components A and B are to be balanced in terms of
their reactive equivalents for an RMA reaction. The equivalent
molar ratio of C--H acceptor to donor groups in the composition is
generally between 3:1 and 1:6, preferably between 2:1 and 1:4, more
preferably between 3:2 and 1:3, most preferably less than 1:1 and
preferably more than 1:2. Component A is typically present in the
composition in weight fractions between 5 and 95 wt % (relative to
total resin solids), component B is also typically present in the
composition in weight fractions between 5 and 95 wt %. In the
situation that A and B are present in the same polymer, the weight
fraction of this polymer in the composition can be at least 80, 90
or 95 wt % and can even go up to 99 wt %.
Typically, at least one of the components A and B are in the form
of a polymer, for example, a polyester containing malonate groups.
It is also possible that both functional groups (associated with
components A and B) can be present in the same polymer. It is noted
that the term components A, B, C, D and F refers to the compound
having the specified RMA reactive groups without specific regards
to the molecular architecture. A component can be a small single
molecule, a dimer, trimer or tetramer etc or a oligomer or a
polymer chain to which one or more of the specified RMA reactive
groups are attached. For example, Component A can be a single
molecule with a single activated methylene moieties like malonate
or ethylacetoacetate. These molecules have two acidic C--H donor
groups available for RMA reaction. Component A can also be a dimer
or trimer comprising 2 or 3 malonates. Component A can also be an
oligomer or polymer chain comprising one or more malonates, for
example attached to or incorporated in the chain. The same applies
in fact to components B, C, D and F. Moreover, one or more of the
components A, B, C, D and F can be combined in a small molecule,
oligomer or polymer. The particular choice of the form of the
components depends on the envisaged characteristics of the
cross-linked network to be formed. Also different polymers can be
used in combination in the composition, for example a polyester,
polyepoxy, polyurethane or polyacrylate polymer. It is also
envisaged to use combinations of different polymers which are
integrated by the RMA reaction in the cross-linked network. It is
noted that components C, D and F may also comprise two or more
acidic donor groups that are Michael addition donor reactable with
component B and therefore can be integrated into the cross-linked
network. In general the molecular weight of the oligomer or
polymers carrying components A to F can vary between wide ranges,
the choice depending on the particular application envisaged;
typically the (weight averaged) molecule weight Mw is higher than
100, 200 or 500 and lower than 200,000, 150,000, 100,000 or 50,000
gr/mol. As described herein for coating applications the number
average molecular weight (Mn) is preferably in the range of from
about 100 to about 5000.
Preferably, the composition does not comprise substantial amounts
of acidic components other than components A, C, D and F that are
able to inhibit Michael Addition reaction between components A and
B.
Component C is a salt according to formula Cat.sup.+ X.sup.-,
wherein Cat.sup.+ is a non-acidic cation, with no ability to
inhibit the crosslinking reaction of components A and B. This
implies that, if any protons are associated with the cation, their
acidity does not exceed that of the dominant C--H functions in
component A, by more than two units, preferably not more than 1 and
more preferably not more than 0.5 pKa unit. Examples of useful
cations include inorganic cations, preferably alkaline or alkaline
earth metal cations, more preferably K+, Na+ and Li+, or organic
cations like tetraalkylammonium and tetraalkylphosphonium salts,
but also cations that do have a proton but are extremely
non-acidic, for example protonated species of strongly basic
organic bases as e.g. DBU, DBN or tetramethylguanidine. These bases
would be able to initiate the crosslinking reaction between
components A and B but do not interfere with the reaction
(inhibiting) in their protonated form. An additional advantage of
the invention is that component C can be significantly less
expensive than the known RMA latent base catalyst. For example, in
most circumstances the cations that are required in carbondioxide
blocked latent base catalyst are of the tetraalkylammonium type
which are much more expensive. Because of the anion X-- the salt
component C has sufficient solubility even with simple and
inexpensive cations like potassium.
Basic component(s) C is a salt of a basic anion X-- from an acidic
X--H group containing compound wherein X is N, P, O, S or C. The
anion X-- of component C is essential for the invention. The anion
X-- must be a Michael Addition donor reactable with component B and
it is an anion of a corresponding acid X--H that is significantly
more acidic than the dominant reactive C--H species of component A.
In particular, the anion X-- is characterized by a pKa(C) of the
corresponding acid X--H of more than two units lower than the
pKa(A) of the majority component A and being lower than 10.5. If,
for example, that dominant component A species is a malonate (pKa
13), the pKa of X--H should be lower than 10.5. Preferably, it is
lower than 10, more preferable lower than 9.5, even more preferably
lower than 9, most preferably lower than 8.5. If the dominant C--H
species of component A is of another nature (e.g. acetoacetate, pKa
10.7), the pKa of X--H should be at least two units lower than that
of the dominant component A C--H species. Component C can comprise
more than one different component within the ranges specified.
Furthermore, it is important that X-- is reactive with component B
according to a Michael addition reaction, through the site where
the acidic proton may be attached. Upon such reaction, the original
X-- anion is thus converted into a carbanion of higher basicity,
with loss of the ability to reform an X--H species.
Finally, it is important that the reactivity of species X-- towards
component B is lower than that of the anion of the dominant C--H
species of component A. This ensures that an effective induction
time can be created. Preferably, the reactivity is lower by a
factor of at least 3, more preferably 5, more preferably at least
10, even more preferably at least 20, even more preferably at least
40, most preferably at least 100. The reactivity however should
also not be too low, since otherwise reaction completion will be
too slow; the reaction should not be slower than that of the anion
of component A by a factor more than 10,000, preferably not more
than 5,000, more preferably not more than 2,000, even more
preferably not more than 1,000, most preferably not more than
500.
Component C is present in an amount of at least 1 peq/g
(microequivalent per gram organic solid components), preferably
more than 5 peq/g, more preferably more than 10 peq/g, and
preferably not more than 1 meq/g, more preferably no more than 600
peq/g, most preferably no more than 400 peq/g. The term organic
solid components refers to the solid resin forming components, also
referred to as binder in a coating composition, excluding volatile
components, pigments, sag control agents, and other paint typical
paint additives. In particular, amounts are expressed in relation
to the sum of components A, B, C, and optional D and F that react
to form the crosslinked network. Component C is the dominant basic
component present, eventually being able to initiate (following a
cascade of acid-base reaction steps the reaction of component A and
B. Preferably no significant amounts are present of other basic
species being able to directly, or after unblocking a carbon
dioxide, initiate the reaction between components A and B, without
being consumed in a Michael addition reaction (and do not form a
covalent bond) with component B. Component C can be an low
molecular weight species, but it can also be part of a polymeric
species, and it can be combined with component A and/or D in a
polymer.
It is preferred that besides component C, also a component D is
present to allow longer pot lives. For some applications, fast
activation upon mixing may present no problems (or even be
preferred), for others a longer workability window is required
following mixing. Component D is an acidic component X'--H that is
similar in characteristics to the corresponding acid X--H of the
anion of component C. X' can be the same as X, or it can be
different; component D can also comprise multiple species according
to the definition. Thus, the pKa of component D is defined by being
lower than 10.5 and being 2 units lower than pKa(A). Preferably, it
is lower than 10, more preferable lower than 9.5, even more
preferably lower than 9, most preferably lower than 8.5. Also if
the dominant C--H species of component A is significantly lower
than malonate (e.g. acetoacetate, pKa 10.7), the pKa of X'--H
should be at least two units lower than that of the dominant
component A. In general, the pKa of X'--H of component D will not
be lower than that of the X--H species related to component C,
since otherwise, an acid shift would reverse the roles of X and X'
species, as will be recognized by those skilled in the art. X'--,
upon deprotonation of component D, is reactive with component B
according to a Michael addition reaction, through the site X' where
the acidic proton is attached. Upon such reaction, the original
X'-- anion is thus converted into a D-B adduct carbanion of higher
basicity, with loss of the ability to reform an X--H species.
The reactivity of species X'-- towards component B is lower than
that of the anion of the dominant C--H species of component A. This
ensures that an effective induction time can be created.
Preferably, it is lower by a factor of at least 3, more preferably
5, more preferably at least 10, even more preferably at least 20,
even more preferably at least 40, most preferably at least 100. The
reactivity however should also not be too low, since otherwise
reaction completion will be too slow; the reactivity should not be
lower than that of the anion of component A by a factor more than
10,000, preferably not more than 5,000, more preferably not more
than 2,000, even more preferably not more than 1,000, most
preferably not more than 500. The same reactivity preference
applies to anion X-- in component C.
Component C can be prepared by an acid-base reaction of a strong
base and a component X--H. Component D (X'--H) can be separately
added or, in case the anions X and X' or chosen the same, component
D can also be formed in combination with component C by reacting a
strong base with a molar excess of component D (X--H) to form a
mixture of a salt of the anion of X--H as Component C and the
remaining unreacted excess X--H as Component D. Evidently, it is
possible to add an additional X'--H components D in which X' is not
the same as the original X--H from which component C is formed. In
such a combination, it is preferred in view of improving pot life
that the total molar amount of the original X--H and X'--H species
exceed that of the original strong base used.
Component D delays the cross-linking reaction between component A
and B in the composition and creates an induction time. This also
provides open time in application of a coating layer of the
cross-linkable composition; open time being the time that the
viscosity is low enough to flow and allow entrapped air to escape
and solvent to evaporate. A large amount and low activity of
component D provides a longer induction time/delay. The preferred
equivalent amount of component D in the composition can be defined
as a function of the equivalent amount of the anion X-- in
component C. The preferred molar ratio Rd/c of component D over
basic anion X-- in component C is dependent on the relative
reactivity of the corresponding anion X-- towards component B
relative to anions of component A. The lower this relative
reactivity of component C compared to A, the lower the preferred
ratio can be to provide a good open time; if this relative
reactivity is higher, the ratio will be higher. In general, we need
at least 1 equivalent % of component D compared to component C,
preferably more than 10%, more preferably more than 50%, even more
preferably over 100%; preferably it is no more than 5000%, more
preferably no more than 4000, 3000, 2000, 1000 or 500%.
As described above, components C and D can also be combined in one
molecule. An example of such alternative embodiment is a molecule
comprising a functional group containing more than one acidic X--H
that is Michael Addition reactive with B, as would for example be
the case for a 1,3-diketone, or nitromethane. A salt of such a
material wherein one or more of the acidic X--H groups is in anion
form, would be considered to contribute one or more equivalent of
component C, but the other one or more not deprotonated X--H groups
would provide one or more equivalents (for example nitromethane 2,
and barbituric acid 3) of non-deprotonated X'--H species able to
react with component B through Michael addition (component D). An
example of such a molecule having both component C and D is a
mono-salt of a compound of formula 1 wherein R.dbd.H. This salt has
one acidic proton C--H as component D and one salt component C
wherein X=X'. One equivalent of such a salt of a
(mono-deprotonated) X--H would react with component B, followed by
deprotonation of the second remaining acidic group (X'--H). This is
analogous to a situation wherein C and D are separate and component
C as a salt of a single X--H group reacts with Michael addition
with B followed by deprotonation of an X'--H on another separate
component D. A salt of acidic methylene or methyl groups containing
multiple acidic hydrogens should be considered to contribute to
both component C and D for example in a ratio 1:1 in case of
methylene or ratio 1:2 in the case of nitromethane.
Component D can be present as low molecular weight species, it can
be present as a polymer, it can be present in a molecule alongside
the functionality of component C, as discussed in the previous
paragraph, it can also be combined with component A in a polymeric
substance, it can be combined with component B in as substance, and
it can be part of a material in which the functionalities A, C and
D are combined. It is possible that the composition contains less
than 30 wt % to resin of other components able to undergo Michael
addition reaction with component B not covered by the definitions
of components A and D.
The pKa values referred to, are aqueous pKa values at ambient
conditions (21.degree. C.). They can be readily found in literature
and if needed, determined in aqueous solution by procedures known
to those skilled in the art. A list of pKa values of relevant
components is given below.
TABLE-US-00001 Succinimide 9.5 Isatine 10.3 Ethosuximide 9.3 Uracil
9.9 Phthalimide 8.3 4-nitro-2- 9.6 methylimidazole 5,5-dimethyl
10.2 Phenol 10.0 hydantoin 1,2,4-triazole 10.2 Ethylacetoacetate
10.7 1,2,3-triazole 9.4 ethyl cyano-acetate 9.0 benzotriazole 8.2
acetylacetone 9.0 benzene-sulfonamide 10.1 1,3-cyclohexanedione 5.3
nitromethane 10.2 Saccharin 2.0 nitroethane 8.6 barbituric acid 4.0
2-nitro-propane 7.7 diethylmalonate 13.0
The relative reactivities in Michael addition of components A, C, D
and F towards B and referred to can be determined experimentally.
The reactivity of the anions of various X--H species can be derived
from model experiments when either is tested under comparable
conditions in a formulation at room temperature with excess of
model RMA acceptor groups B (e.g. butylacrylate), and in presence
of a base at least able to deprotonate 1 mole % of the RMA donor.
The consumption of acidic species can be followed in time by
titration, NMR, GC or other suitable analytical methods known to
those skilled in the art.
Suitable components X--H (from which component C salts can be
derived) and X'--H (components D) can be acids in which the acidic
proton is attached to a C, N, P, O or S atom, and the Michael
Addition reactivity takes place through these atoms. Preferably, it
is attached to a C, N or P atom, most preferably a carbon or
nitrogen atom. The X and X' in components C and D preferably are
each independently chosen to be C, N or P.
Suitable compounds C and D have X-- or X'--H originating from
methine or methylene activated by two or three substituents, these
substituents being selected from --CO2R ester groups, C(.dbd.O)R
ketone groups, cyano groups and nitro groups, or a methyl,
methylene or methine group activated by one nitro group. Examples
of components that are suitable, as component D, or in their anion
form, as part of component C, are cyanoacetates, 1,3-diketones as
acetylacetone and 1,3-cyclohexanedione as well as their substituted
analogs as dimedone, and nitroalkanes as nitromethane, nitroethane
of 2-nitropropane. A preferred class of X--H and X'--H components C
and D are compounds wherein the X from component C, and/or the X'
in component D is a carbon-acidic compound (X=C); methine,
methylene and methyl groups activated by electron withdrawing
substituents as CO2R esters, ketones, cyano groups and nitro
groups, in particular components according to formula 1. Usually,
at least two of such substituents need to be present, although in
the case of nitro groups, one substituent can suffice.
Another preferred class of X--H and X'--H components comprise
compounds wherein the X from component C, and/or the X' in
component D is an aza-acidic compound (X=N), preferably these N--H
acidic compounds are derived from an Ar--NH--(C.dbd.O),
--(C.dbd.O)--NH--(C.dbd.O)--, or a --NH--(O.dbd.S.dbd.O)-- group or
a heterocycle in which the nitrogen of the N--H group is contained
in a heterocyclic ring. Preferred components can be found in the
class of imide components, preferably (optionally substituted)
cyclic imides, as succinimide and ethosuximide. Substituted
hydantoins, uracils and barbiturates also fall in this category.
Another suitable class is formed by aromatic sulphonamides, as
benzenesulfonamide and p-toluenesulfonamid. Saccharine is a low pKa
example in this category.
Another preferred class of X--H and X'--H components comprise N--H
acidic compounds derived from heterocycles containing the N--H as
part of the heterocyclic ring. Examples are triazoles, pyrazoles
and imidazoles, e.g. 2-methyl-4-nitro-imidazole. Especially
preferred are triazole components as 1,2,4-triazole and
benzotriazole.
It was found that it can be beneficial in view of creating both a
high reactivity in combination with a long pot life and open time
if there are more than one different groups involved in the
composition as X--H (related to component C) and X'--H (component
D). The inventors have found that it is favourable to use a
combination of one or more X--H or X'--H groups having a pKa<8.9
and other X--H or X'--H groups having a pKa>8.9; they have also
found that it is favorable to combine a component from the
aza-acidic compounds, in particular the triazoles, with imides or
activated methylenes as 1,3-diketones. Preferably in the
crosslinkable composition the pKa(C) is lower than 8.9 and pKa(D)
is higher than 8.9.
Preferably in the crosslinkable composition a. more than 50,
preferably more than 60, 70 or even more preferably more than 80%
of the RMA donor groups in components A are from malonate groups,
b. more than 50, preferably more than 60, 70 or even more
preferably more than 80% of the RMA acceptor groups in components B
are from acryloyl groups, c. component C is a benzotriazolide salt,
a salt of 1,2,4-triazole or a salt of 1,3-cyclohexanedione, d.
component D is benzotriazole or a triazole, a 1,3-diketone, or an
imid.
The composition may further comprise as Component(s) E one or more
thixotropy inducing additives, in particular sag control agents for
use in coating applications and in particular in thick layers.
The crosslinkable composition may further comprise preferably minor
amounts of component(s) F comprising an acidic X''--H group wherein
X'' is N, P, O, S or C, which is i) different from components A and
D but also a Michael addition donor reactable with component B.
These components could for example be components with the same pKa
range as components A but that do not have at least 2 reactive
groups for forming a crosslinked network, components C or N--H
acidic component(s) having a pKa above 10.5, for example pyrazoles
and imidazoles. Such component may be used to moderate reactivity
of component A to improve open time. The amount xf of component(s)
F is at most 30 wt %, more preferably at most 25, 20, 15 and
preferably between 1-10 or 1-5 wt % relative to the total weight of
resin forming components A, B, C, D and F.
The cross-linkable composition as described above will generally
not be commercially available because the pot life is generally too
short; the time in which the composition can be handled before
viscosity increase or gelation make this impossible is too short.
Therefore, the crosslinkable composition needs to be completed by
mixing the constituent components A to F shortly before
application. The invention therefore also relates to kits of parts
wherein the parts comprise combinations of the constituent
components of the crosslinkable composition that do not react.
In particular the kit of parts for the manufacture of the
composition according to the invention comprises 1) a part I.1,
comprising component(s) C and a part II.1 not comprising
component(s) C or alternatively 2) a kit of parts comprising a part
I.2 comprising component B and a part II.2 not comprising component
B or alternatively 3) a kit of parts comprising part I.3 comprising
instead of component C the corresponding acidic compound X--H and a
part II.3 comprising a strong base for mixing with part I.3 to
convert the acidic compound X--H to its corresponding salt
component C.
The inventors have found that a preferred way of combining the
components of the cross-linkable composition, is to provide one
part I.1 comprising component C, preferably in a part of the
solvent if needed and preferably also at least part of component D
and a separate part II.1 not comprising components C and comprising
components A, B and optionally D and F. The invention also relates
to a kit of parts I.1 and II.1 as described. The invention also
relates to a method of forming the crosslinkable composition by
adding kit part I.1 containing component C to a composition
containing component A or B.
An alternative way of combining the components to form the complete
crosslinkable composition is by having a part I.2 in which
component A and component C (and optionally component D) are
combined but not component B and a part II.2 and comprising
component B, which parts II.1 and II.2 can be combined shortly
before use. The invention also relates to a kit of parts II.1 and
II.2 as described and to a method for the preparation of the
cross-linkable composition comprising the mixing of parts II.1 and
II.2.
A third useful way or preparing the crosslinkable composition, is
by providing a composition comprising components A, B and
optionally D and F, and instead of adding component C as salt,
adding the corresponding acid component X--H followed (shortly
before application) by the addition of a strong base which forms
the component C salt in situ. The same can be achieved if X--H is
added in molar excess to the strong base leaving residual X--H as
component D. This method requires proper mixing routines, for
example dilution of the strong base and/or intense stirring/mixing,
so that salt formation can occur before unintended (local)
initiation of the RMA reaction of components A and B. This
component X--H can also be added shortly before the application of
the cross-linkable composition. Optionally the salt component C is
formed ex-situ shortly before application by reacting the component
X--H with a strong base and adding to the remaining components of
the cross-linkable composition. The invention therefore also
relates to a part I.3 comprising components A, B and optionally D
and F, and instead of component C as salt the corresponding acid
component X--H. The invention also relates to its use for the
preparation of a cross-linkable composition according to the
invention, to a kit of part comprising part I.3 and a separate part
II.3 comprising a strong base and to the process comprising mixing
of part I.3 and II.3. The invention also relates to compositions
obtained by the processes mixing of components A to C and
optionally D, E and F in any particular order, preferably in an
order as above described. The invention also relates to a method of
preparing a crosslinkable composition comprising providing a first
composition comprising components A, B, optional D and F but not
component C and, just before use of the crosslinkable composition,
forming component C by reacting a strong base with an X--H
containing component either in-situ in the first composition or
ex-situ followed by mixing of the thus formed component C with the
first composition.
It is noted that in the composition pK(D) is higher than pK(C).
However, when component C and D are separate in a kit of parts,
this is not required because on mixing an acid-base reaction will
take place between X'--H (D) and X(--) (C) and in equilibrium there
will be X--H and X'(--) in the crosslinkable composition.
The crosslinkable composition according to the invention can have a
gel time at room temperature of more than 20 minutes. For many
applications, upon completing preparation of the crosslinkable
composition, the resulting composition has preferably a gel time,
before application, at room temperature of more than 20 minutes,
more preferably more than 30 minutes, more preferably more than 60
minutes, most preferably more than 90 minutes. A method for
measuring the gel time is described below. The crosslinkable
composition can be cured at various temperatures, and it is also
possible and advantageous to do so at low temperatures which are
usually the most challenging. The composition can be cured at
temperatures less than 120, preferably less than 100, 80, 60, 50,
40 and even less than 30.degree. C.
The cross-linkable composition according to the invention comprises
network forming components A, B, C, preferably also D and
optionally F and optionally comprising solvent, said composition
preferably having a. Component(s) A, preferably an oligomer or
polymer, in an amount xa between 5 and 95 wt % relative to total
resin and b. component(s) B, preferably a dimer, trimer or
tetramer, oligomer or polymer, in an amount xb between 5 and 95 wt
% relative to total resin, wherein xa plus xb is at least 40,
preferably 50, 60, 70, 80 or 90 wt % relative to total resin, c.
basic component(s) C in an amount xc between 0.001 and 1 meq/(gr
total resin), d. preferably component(s) D in an amount xd such
that the equivalent ratio Rd/c of acidic X'--H groups in component
D over basic anion groups X-- in component C is between 1% and
5000%, e. optional component(s) F in an amount xf between 1 and 30
wt % relative to total resin, f. optionally a solvent in an amount
between 0.1 and 80 wt % relative to total weight of total resin
plus solvent.
Depending on the envisaged application, the crosslinkable
composition may also contain a certain amount of one or more
different solvents, preferably organic solvents. In coating
applications it may be preferred to add organic solvents,
preferably less than 80 wt %, more preferably less than 55, 45, 35,
25 wt %. In view of creating a better pot life it is preferred that
the solvent comprises at least 1 wt % of volatile primary alcohols,
more preferably at least 3 wt %, even more preferably at least 5 wt
%, most preferably at least 8 wt %, volatile primary alcohols
(relative to total weight of ABCD and F and solvent). The boiling
point of the volatile primary alcohols is preferable less than
140.degree. C., more preferably less than 130, 120, 110 and most
preferably less than 100.degree. C. Examples include methanol,
ethanol, n-propanol, n-butanol, n-pentanol. The crosslinkable
composition can also contain water.
The invention makes possible to provide substantially solvent free
crosslinkable compositions for special applications. Such special
embodiments are for example powder coat resins or resin for
composite materials. Because the molecular weight of the components
A, B, C, D and F can be chosen very low, the viscosity of the
composition can be low enough for applications requiring a low
viscosity even without a solvent. Low molecular weight components A
to F (Mw<500, 400, 300 or 200) can be used reactive diluent. For
example mono-acetoacetate or mono-malonate can be used as reactive
diluent components A. The advantage is that the composition has a
very low content of volatile organic components (VOC) which
presents a significant environmental advantage. Therefore, in one
of the preferred embodiments the amount of added organic solvent is
low and the VOC is less than 5, more preferably less than 3, 2 or
even 1 wt %. In this embodiment, it is preferred that the resin
components A, B, C, D or F have a molecular weight Mw lower than
50,000, 20,000, 10,000, 5000 or even lower than 3000 gr/mol. This
composition can advantageously be used in applications in which VOC
evaporation is impossible or difficult or unacceptable.
The components A, B, C, D and F all react with each other and
become integrated into the cross-linked network. As described above
components A and B have at least two cross-linked functional groups
(the RMA donor and acceptor groups respectively) to form the
cross-linked network. Preferably at least one of components A or B
have average more than 2, preferably at least 2.1 crosslink
functional groups to provide a more densely cross-linked network.
Apart from components A and B, also each of components C, D and F
may comprise two or more RMA donor groups so they become fully
integrated in the cross-linked network. In general the total amount
of components that have two or more cross-linking groups and hence
can become fully integrated in the cross-linked network represents
at least 40, more preferably at least 50, 60 and 70 and most
preferably at least 80 wt % of the total weight of components A, B,
C, D and F. However, it is preferred that components A and B form
the majority of the cross-linked network, preferably at least 50,
60 or 70 and most preferably at least 80 wt % of the total weight
of resin components A, B, C, D and F.
Moreover, the crosslinkable composition may contain other
components relevant to the specific application intended. These can
be rheology additives to induce thixotropy to allow vertical
application of coatings without sagging; the cross-linkable
composition for use as coating composition can include all sorts of
coating additives like pigments, extenders, nanoparticles, fibers,
stabilizers, dispersants, wetting additives, defoaming additives,
blowing agents etc.
The crosslinkable composition according to the invention can be
used as coating compositions, for coatings in the field of e.g.
metal or wood coatings, plastic coatings, automotive coatings,
marine and protective applications, either pigmented or as clear
coat. It can also be useful for applications in the field of inks,
films, adhesives, foams and composites (as composite matrix). The
invention therefore also relates to coating compositions comprising
the crosslinkable composition according to the invention and
further paint additives, preferably a thixotropy control agent and
to composite articles comprising a filler material, preferably
fibers or particles, more preferably inorganic fibers or particles
and as a binder material the crosslinked composition according to
the invention.
The foregoing more general discussion of the present invention will
be further illustrated by the following specific examples, which
are exemplary only.
The following abbreviations were used for chemicals used in the
experiments: DiTMPTA is di-trimethylolpropane-tetraacrylate
(obtained from Aldrich (MW=466 g/mol)) or used as Sartomer SR355
(supplied commercially by Sartomer); Disperbyk 163 is a dispersant
commercially supplied by Byk; Byk 310 and 315 are additives
commercially supplied by ByK; Kronos 2310 is a TiO2 pigment
commercially supplied by Kronos, TBAH is tetrabutylammonium
hydroxide, TPAH is tetrapropylammonium hydroxide, DBU is
1,8-diazabicyclo[5.4.0]undec-[7]-ene, CHD is 1,3-cyclohexanedione,
EtAcAc is ethyl acetoacetate; RT is room temperature, BT is
Benzotriazole, KBZT solution is solution of potassium
benzotriazolide in ethanol as described below.
Preparation of Malonate Polyester A
Into a reactor provided with a distilling column filed with Raschig
rings were brought 17.31 mol of neopentyl glycol, 8.03 mol of
hexahydrophthalic anhydride and 0.0047 mol of butyl stannoic acid.
The mixture was polymerised at 240.degree. C. under nitrogen to an
acid value of 0.2 mg KOH/g. The mixture was cooled down to
130.degree. C. and 10.44 mol of diethylmalonate was added. The
reaction mixture was heated to 170.degree. C. and ethanol was
removed under reduced pressure. The nearly colourless material was
cooled down and diluted with 420 g of butyl acetate to a 90% solid
content. The final resin had an acid value of 0.3 mg KOH/g solids,
an OH value of 20 mg KOH/g solids and a weight average molecular
weight of 3400 Da.
Preparation of Base Solution C
An amount of acid (X--H) was dissolved in a solution of strong base
in an alcoholic solvent according to Table A (amounts in gram; all
molar ratios strong base/acid are equal to 1). The solution was
left overnight before use.
TABLE-US-00002 TABLE A Base Type strong Amount Amount code base
strong base Type acid acid Ethanol C1 KOH 7 Benzotriazole 14.86 63
C2 TBAH 40% in 5 Benzotriazole 0.92 0 MeOH C3 KOH 1 1,2,4-triazole
1.23 9 C4 DBU 0.50 Benzotriazole 0.39 2 C5 TPAH 40% in 1
Benzotriazole 0.23 0 water C6 KOH 0.86 CHD 1.72 8 C7 tributylamine
1 Benzotriazole 0.64 4
The foregoing more general discussion of the present invention will
be further illustrated by the following specific examples, which
are exemplary only.
Molecular weights were measured by GPC in THF, and expressed in
polystyrene equivalent weights.
Gel time determination: After mixing the base C with the
cross-linkable formulation, the formulation was checked visually at
regular intervals for viscosity increase and heat development. The
gel time was defined as the time needed to stop 10 g of
cross-linkable formulation in a 40 ml vial from displaying any
movement when the vial was turned upside down.
Drying time determination: Paint was sprayed on a 19.times.10.5 cm
phosphate pre-treated steal panel using a Devilbiss spraygun,
nozzle FF-1.4 with an air pressure of 3.5 bar giving a dry film
layer thickness between 67 and 91 .mu.m. Directly after spraying,
the paint was checked regularly (typically every 2-5 min) manually
for tackiness under climatised conditions (22.degree. C., 60.+-.2%
relative humidity). When the film did not display any tackiness any
more upon manual touching, the film was checked for skin-formation
and through-drying by touching with greater force and rotation. If
no mark was observed after this determination, the paint was
defined as dry and the drying time was recorded.
Persoz hardness measurement: Persoz pendulum hardness was measured
in a climatized room at 23.degree. C., and 55+/-5% relative
humidity. Hardness is measured with a pendulum acc. Persoz as
described in ASTM D 4366. Layer thicknesses were measured with a
Fischer Permascope MP40E-S in fivefold on different places on the
panel and averaged.
Wavescan analysis: The panels as described above were analyzed
using the Wavescan II of Byk instruments. Data were stored using
Autochart software from Byk. Analysis was done in the direction
perpendicular to the thickness gradient. In this instrument the
light of small laser diode is reflected by the surface of the
sample under an angle of 60.degree., and the reflected light is
detected at the gloss angle (60.degree. opposite). During the
measurement, the "wave-scan" is moved across the sample surface
over a scan length of approx. 10 cm, with a data point being
recorded every 0.027 mm. The surface structure of the sample
modulates the light of the laser diode. The signal is divided into
5 wavelength ranges in the range of 0.1-30 mm and processed by
mathematical filtering. For each of the 5 ranges a characteristic
value (Wa 0.1-0.3 mm, Wb 0.3-1.0 mm, Wc 1.0-3.0 mm, Wd 3.0-10 mm,
We 10-30 mm) as well as the typical wave-scan-values longwave (LW,
approx. 1-10 mm) and shortwave (SW, approx. 0.3-1 mm) is
calculated. Low values mean a smooth surface structure.
Additionally a LED light source is installed in the wave-scan DOI
and illuminates the surface under 20 degrees after passing an
aperture. The scattered light is detected and a so-called dullness
value (du, <0.1 mm) is measured. By using the three values of
the short wave range Wa, Wb and du a DOI value is calculated. (see
Osterhold e.a., Progress in Organic Coatings, 2009, vol. 65, no 4,
pp. 440-443).
TABLE-US-00003 TABLE B Code Ex 1 Ex 2 Ex 3 Ex 4 Ex 5 Ex 6 Malonate
polyester resin (A) 10 10 10 10 10 10 Sartomer SR355 (B) 5.81 6.46
5.81 6.46 7.02 7.02 EtAcAc (A) 0 0.35 0 0.35 0.35 0.35
Benzotriazole (D) 0 0 0 0 0.57 0 1,2,4-triazole (D) 0 0 0 0 0 0.33
Base-solution type (C) C1 C1 C3 C3 C1 C3 Base solution amount (C)
2.93 3.26 2.72 2.72 3.26 3.02 Gel time (min) 3 5 3 3 28 9
Cross-linkable formulations were prepared according to Table B
(amounts in gram). Components A, B and D were added and mixed.
Subsequently, base-solution C was added and the formulation was
mixed again. The gel time was recorded as described above and the
results are included in Table B.
The gel times in the Table clearly demonstrate very fast gelation
was observed when malonate polyester and Sartomer SR355 were mixed
only with base component C (Ex 1,3). It was also noted that the
reaction was highly exothermic. Also, when EtAcAc was added,
gelation was very fast, despite the somewhat lower functionality
(Ex 2,4). Interestingly, when an excess of component D was added
(Ex 5,6), a significant delay of the gelation was observed. The
delay was larger when component D was benzotriazol compared to when
component D was 1,2,4-triazol, most likely because of the lower
reactivity of benzotriazolide as Michael donor.
TABLE-US-00004 TABLE C Code Ex 7 Ex 8 Ex 9 Ex 10 Ex 11 Comp 1
Malonate polyester resin 10 10 10 10 10 10 (A) Sartomer SR355 (B)
6.46 7.02 7.02 6.0 6.0 6.0 EtAcAc (A) 0.35 0.35 0 0 0 0
Benzotriazole (D) 0 0.57 0.57 0.18 0 0 Base-solution type (C) C2 C2
C5 C4 C6 C7 Base solution amount (C) 3.68 3.68 2.99 2.89 3.31 4.54
Gel time (min) 4 28 35 37 .+-.750 No gel
Cross-linkable formulations from Table C were prepared and tested
in a similar way compared to the formulations in Table B.
Comparison of examples Ex 7-9 show that salts with other cations
neutral in the RMA reaction can be used as initiators to achieve
gelation of these formulations. Again, addition of an excess of
component D (benzotriazole) resulted in longer gelation times.
The salt of nitrogen base DBU and benzotriazole resulted in a
similar observation (Ex 10), i.e. gelation occurred in a similar
time as observed for other samples containing component D.
Interestingly, if a weaker nitrogen base was used, such as
tributylamine, no gelation was observed (Comp 1). This could be
explained by the higher acidity of the tributylammonium cation
compared to DBU-H+, i.e. the first significantly inhibited
deprotonation of malonates, whereas the latter did not.
A special case is the use of 1,3-cyclohexanedione (Ex 11), because
this compound has two acidic CH bonds. In its form as
mono-potassium salt, one acidic and potentially RMA reactive CH
bond will still be present. Therefore, it will act both as
component C and as component D. This compound could also be used to
initiate gelation of this cross-linkable composition. However,
because of its low pKa-value and potential low reactivity in RMA
reactions, a long gelation time was found.
TABLE-US-00005 TABLE D Code Ex 12 Ex 13 Ex 14 Ex 15 Ex 16 Ex 17
Kronos 2310 125.28 125.28 125.28 127.71 126.92 125.28 Disperbyk 163
3.77 3.77 3.77 3.84 3.82 3.77 Sartomer SR355 (B) 59.62 59.62 59.62
60.77 60.40 59.62 Malonate polyester resin (A) 100 100 100 100 100
100 Sartomer SR355 (B) 8.51 8.51 8.51 10.4 9.8 8.51 EtAcAc (A) 3.47
3.47 3.47 3.47 3.47 0 Byk 310/315 (1:4 by mass) 0.94 0.94 0.94 0.96
0.95 0.92 Benzotriazole (D) 3.11 3.11 3.11 6.22 5.71 0.87 Acetyl
acetone (D) 0 5.23 10.45 10.45 9.6 0 Succinimide (D) 0 0 0 0 0 0.31
n-Propanol 27.5 27.9 26.3 26.95 26.5 14.69 Ethanol 0 0 0 0 0 13.50
Butyl acetate 27.5 27.9 26.3 26.95 26.5 0 KBZT solution (C) 35.5
35.5 35.5 35.5 32.6 17.71
TABLE-US-00006 TABLE E Dry layer thickness (.mu.m) 90 91 85 87 67
69 Drying time (min) 37 46 50 65 45 60 Gel time (min) 30 42 55 72
60 n.d. Hardness after 24 h RT 116 109 115 68 138 109 Shortwave 6.7
4.6 5.0 4.0 7.8 31.7 Longwave 2.5 3.2 3.7 2.4 4.8 4.7
Example formulations Ex 12-17 were prepared as pigmented paints,
having compositions as tabulated in Table X (amounts in grams).
The pigmented paint was prepared by first milling Kronos 2310,
Disperbyk 163 and Sartomer SR355 together to a pigment paste (first
3 components from table D). The KBZT solution was obtained by
dissolving 7 g of KOH and 14.86 g of benzotriazole (1:1 molar
ratio) in 63 g of ethanol, yielding a 1.47 meq/g solution of
potassium benzotriazolide. To the pigment paste, malonate resin,
more Sartomer SR355, EtAcAc, Byk 310/315 mix, Benzotriazole, acetyl
acetone, n-propanol and butyl acetate were added in amounts
according to Table D. All components were mixed. Subsequently, the
KBZT solution was added, the now ready-to-spray paint was mixed and
sprayed as described above within 5 minutes after addition of the
KBZT solution.
Dry layer thickness (.mu.m), drying time (min), gel time (min),
hardness after 24 h RT, shortwave and longwave were measured on
these formulations as described above. Results are included in
Table E.
It can be observed from comparison of examples Ex 12, 13, 14 that
increasing the amount of acetyl acetone in the formulations
resulted in increased drying times as well as longer gel times,
without affecting the hardness too much. Comparison of Ex 14 and Ex
15 demonstrates that increasing the level of benzotriazole further
delayed the drying and gel time. However, when a very similar
formulation (Ex 16), containing less KBZT solution compared to Ex
15, was applied at a lower layer thickness, good results were
obtained with respect to drying time, drying/gel time balance and
hardness. Finally, Ex 17 shows that succinimide is very effective
in extending the drying time, but this resulted in a high shortwave
value.
Example 18. Determination of Michael Addition Reactivity of
Succinimide
5 grams of succinimide (50.5 mmole) were dissolved in a mixture of
42 grams of butyl acrylate and 42 grams of methanol, and maintained
at room temperature as such, or after adding a strong base (9.82
grams of a 1.12 meq/g solution of tetrabutylammonium hydroxide in
methanol, 11 meq). Subsequently, the concentration of succinimide
is determined as a function of time by taking samples, neutralizing
with a known excess of HCl in water, and backtitration with a KOH
solution. Without base initiation, no significant loss of
succinimide N--H in this solution is observed in two weeks. With
the base added, the succinimide concentration can be seen to
decrease with time, as illustrated in Table F below. Succinimide
concentration is expressed as % relative to the theoretical level
based on used amounts.
TABLE-US-00007 TABLE F Time (min) Succinimide remaining (%) 3 99 30
87 60 77 120 60 180 48
At this catalyst level ([succinimide]/[base]=5), 23% of the
succinimide acidic protons were consumed in approx. 1 hour.
Using the same method, also the reactivity for various other
components was determined; as a reference a similar set-up was used
for the reactivity of dimethylmalonate under these conditions (only
in this case, the remaining DMM level was determined with GC).
Table G lists the results of the relative Michael addition
reactivities, expressed as a number indicating the initial increase
in % conversion, per minute, under these conditions. It can be seen
that in all cases, this intrinsic reactivity is significantly lower
than that of a malonate, but still present.
TABLE-US-00008 TABLE G Relative conversion rates Dimethylmalonate
42 Succinimide 0.33 Benzotriazole 0.29 1,2,4 triazole 0.91
5,5-dimethylhydantoin 0.03 Benzenesulfonamide 0.11
* * * * *